Showing papers by "University of Seville published in 1972"
TL;DR: A number of studies on the decomposition of formic acid were initiated during the first decade of the present century by Mailhe and Sabatier as discussed by the authors, using metals and metal oxides.
Abstract: Studies on the decomposition of formic acid were initiated during the first decade of the present century by Mailhe and Sabatier [1], using metals and metal oxides. These authors were concerned primarily with the selectivity of their catalysts, i.e., their ability to favor one of the reactions possible for the decomposition of formic acid (Eq. 1).
121 citations
TL;DR: In the green alga Chlamydomonas reinhardi, all the enzymes of the nitrate-reducing system are nutritionally repressed by ammonia as discussed by the authors.
78 citations
TL;DR: Evidence is presented that Chlorella nitrate reductase can exist in two interconvertible forms, active and inactive, according to the redox state of the enzyme, the conversion being affected by temperature and pH.
68 citations
TL;DR: A method for the purification to homogeneity of spinach nitrite reductase is described, as well as some of its most relevant physicochemical properties, i.e. molecular weight, absorption spectrum and metal content.
32 citations
TL;DR: The introduction of the Se atom offers no advantages in the analytical application of these compounds and the complexes of picolinaldehyde selenosemicarbazone with cations in aqueous solution are less stable.
22 citations
TL;DR: It is shown that, in Chlorella, the cellular level of nitrite reductase activity specifically increases in response to the iron content of the culture medium, which is not affected by the concentration of iron in the nutrient solution under the same conditions.
Abstract: In Chlorella, as in most photosynthetic organisms, the reduction of nitrate to ammonia proceeds sequentially in two independent and well characterized steps, catalyzed by the enzymes of the nitrate-reducing system: 1. the reduction of nitrate to nitrite by the flavomolybdoprotein NADH-nitrate reductase, and 2. the reduction of nitrite to ammonia by the ironprotein ferredoxin-nitrite reductase. In this communication, it is shown that, in Chlorella, the cellular level of nitrite reductase activity specifically increases in response to the iron content of the culture medium. By contrast, the activity of nitrate reductase is apparently not affected by the concentration of iron in the nutrient solution under the same conditions.
17 citations
TL;DR: The authors have studied the otolith organization in the macula utriculi of the guinea pig and found ring diagrams that are neater in the dark zones than in the clear ones, which makes them suspect a possible existence of crystalline units in the Otoliths that are randomly oriented.
Abstract: The authors have studied the otolith organization in the macula utriculi of the guinea pig. The electronic diffraction patterns obtained from the otolithic membrane and the embedding material are identical, and the same as the amorphous substances. In the otoliths we have found ring diagrams that are neater in the dark zones than in the clear ones. This finding makes us suspect a possible existence of crystalline units in the otoliths that are randomly oriented.
9 citations
TL;DR: The author demonstrates how there is a direct and proportional relation between the intensity of the stimulus and the amplitude of the E.R.A., for people with normal hearing as well as for patients with transmission or reception hearing loss.
Abstract: The author demonstrates how there is a direct and proportional relation between the intensity of the stimulus and the amplitude of the E.R.A., for people with normal hearing as well as for patients with transmission or reception hearing loss. However, when the stimuli are intense in people with normal hearing the amplitude of the E.R.A. diminishes, and in patients who suffer a hearing loss with recruitment, the E.R.A. reaches a greater amplitude than the intensity of the sonorous stimulus used.
6 citations
TL;DR: An accurate, simple and rapid method for the determination of nitrate within the 10–100 μ M range is described, based on the reduction of nitrates to nitrite with a NADH-nitrate reductase preparation from spinach.
5 citations